1. Field of the Invention
The present invention relates to a rolling mill of a type comprising: an upper work roll and a lower work roll brought into contact with a material to be rolled; an upper backup roll for supporting the upper work roll, a hydraulic jack disposed above the upper backup roll and capable of adding a pressure adjusted in correspondence with the rolling load to the upper work roll via the upper backup roll, a thrust metal block arranged above the hydraulic jack; and a pressurizing screw brought into contact with the upper surface of the thrust metal means to limit the upward movement of it or positioning the upper work roll.
2. Description of the Prior Art
A rolling mill of the type described above is, for example, disclosed in Japanese Patent Unexamined Publication No. 58-163510, in which a space needed for roll exchange is secured by moving, along the carrier rail, the hydraulic jack together with the thrust metal block in the axial direction of the rolls. The hydraulic jack included in this rolling mill comprises a cylinder having an upward cylinder bore formed therein and a ram disposed on the upside of this cylinder and capable of being moved within this cylinder bore. The thrust metal block is disposed above the ram, and a control unit is provided for the cylinder body for the purpose of adjusting the quantity of the hydraulic oil in the space between the cylinder and the ram in accordance with the rolling load.
However, the conventional rolling mill encounters a problem in that a long carrier rail and a large-size and long-stroke cylinder for retracting the hydraulic jack needs to be provided.
Furthermore, the rolling mill is arranged in such a manner that the cylinder of the hydraulic jack is disposed below the ram and is positioned in contact with the upper portion of the upper backup roll chock. Therefore, an impact generated due to the fact that the material to be rolled is caught by the rolling mill or is moved out of the rolls can be directly transmitted to the cylinder of the hydraulic jack via the upper backup roll, causing the control unit provided for this cylinder to be damaged to the life of it to be shortened.